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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

26481 results found.

  1. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  2. GRB 251128A: Fermi GBM Observation
  3. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  4. GRB 251129A: SVOM detection of a burst
  5. SVOM GRB251129A: Global MASTER-Net observations report
  6. GRB 251129A: SVOM detection of a burst
  7. GRB 251126A: Swift-BAT refined analysis
  8. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  9. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  10. Fermi GRB 251128A: Global MASTER-Net observations report
  11. GRB 251127A: Glowbug gamma-ray detection
  12. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  13. GRB 251126A: further SAO RAS optical observations
  14. GRB 251126A NUTTelA-TAO Early Measurements
  15. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  16. GRB251126A: MAO/AZT-22 optical observations
  17. GRB251126A: Continued optical observation from 1.3m DFOT
  18. GRB 251126A: Swift/UVOT Detection
  19. GRB 251126A: Mondy and SAO RAS optical observations
  20. GRB 251126A: Swift-XRT refined Analysis
  21. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  22. GRB 251126A: NOT optical observations
  23. GRB 251126A: 1.3m DFOT optical afterglow detection
  24. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  25. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  26. Fermi GRB 251127A: Global MASTER-Net observations report
  27. GRB 251126A: Enhanced Swift-XRT position
  28. GRB 251126A: Kilonova-Catcher optical afterglow detection
  29. GRB 251126A: Nanshan/HMT optical afterglow detection
  30. Swift GRB 251126A: Global MASTER-Net observations report
  31. GRB 251121A: Fermi GBM Observation
  32. GRB 251126A: GIT discovery of the likely optical afterglow
  33. GRB 251126A: Swift detection of a burst
  34. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  35. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  36. EP251124b: NOT r- and z-band optical upper limits
  37. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  38. Fermi GRB 251125B: Global MASTER-Net observations report
  39. EP251124b: Global MASTER-Net observations report
  40. EP251124b: EP-WXT detection of a fast X-ray transient
  41. EP251124a: Xinglong GWAC-F60A optical observation
  42. Fermi GRB 251125A: Global MASTER-Net observations report
  43. EP251124a: NOT r- and z-band optical upper limits
  44. EP251124a: Global MASTER-Net observations report
  45. EP251124a: Swift-XRT observations
  46. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  47. EP251124a: Optical upper limit with Kinder observations
  48. Fermi GRB 251124a: Global MASTER-Net observations report
  49. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  50. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  51. EP251124a: GROWTH-India Telescope optical upper limits
  52. EP251124a: Einstein Probe detection of an X-ray transient
  53. GRB 251116C: Swift-XRT confirmation of fading
  54. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  55. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  56. EP251118A: 3.6m DOT optical afterglow detection
  57. GRB 251122A / EP251122a: EP-FXT counterpart detection
  58. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  59. GRB 251122A / EP251122a: WFST optical observations
  60. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  61. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  62. GRB 251122A / EP251122a: LCO optical upper limits
  63. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  64. EP251122a: Global MASTER-Net observations report
  65. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  66. GRB 251122A / EP251122a: SVOM detection of a long burst
  67. EP251122a: Einstein Probe detection of an X-ray transient
  68. EP251118a: Continued Optical Detection with Kinder observations
  69. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  70. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  71. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  72. EP251118a: Xinglong-2.16m optical observation
  73. GRB 251115A: Fermi GBM Observation
  74. Fermi trigger No 785388351: Global MASTER-Net observations report
  75. EP251118A: 1.3m DFOT optical afterglow detection
  76. GRB 251118A: Swift/UVOT Detection
  77. EP251118a / GRB 251118C: SAO RAS optical observations
  78. GRB 251118A: Glowbug gamma-ray detection
  79. GRB 251118A: Fermi GBM Observation
  80. GRB 251118A: Swift-XRT afterglow detection
  81. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  82. EP251118a: Optical detection with Kinder observations
  83. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  84. GRB 251118A: NuSTAR detection of bright prompt emission
  85. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  86. GRB 251116C: NOT optical observations
  87. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  88. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  89. GRB 251117A: Swift-XRT observations
  90. EP251118A / GRB 251118C : MASTER optical counterpart observations
  91. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  92. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  93. EP251118a: VLT near-infrared observation
  94. GRB 251116D: SVOM/GRM observation of a long GRB
  95. GRB 251119A: SVOM detection of a possible burst
  96. EP251118a: Global MASTER-Net observations report
  97. LAT GRB251118.86: Global MASTER-Net observations report
  98. EP251118a: NOT candidate optical counterpart
  99. EP251118a: Einstein Probe detected of a fast X-ray transient
  100. Fermi GRB 251118B: Global MASTER-Net observations report

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